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<h1 align=center style='text-align:center'><span lang=EN-US style='border:none windowtext 1.0pt;
padding:0cm;background:white'>1.C</span><span style='font-family:宋体;border:
none windowtext 1.0pt;padding:0cm;background:white'>语言发展过程</span></h1>

<p class=MsoNormal align=left style='text-align:left'><span style='font-family:
宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>前言：Ｃ语言是在</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'> 70 </span><span style='font-family:宋体;
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>年代初问世的。一九七八年由美国电话电报公司</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'>(AT&amp;T)</span><span style='font-family:宋体;
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>贝尔实验室正式发表了Ｃ语言。同时由</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'>B.W.Kernighan</span><span style='font-family:
宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>和</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'>D.M.Ritchit</span><span style='font-family:宋体;
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>合著了著名的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'>“THE C PROGRAMMING LANGUAGE”</span><span
style='font-family:宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>一书。通常简称为《</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>K&amp;R</span><span
style='font-family:宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>》，也有人称之为《</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>K&amp;R</span><span
style='font-family:宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>》标准。但是，在《</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>K&amp;R</span><span
style='font-family:宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>》中并没有定义一个完整的标准</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>C </span><span style='font-family:宋体;color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'>语言，后来由美国国家标准协会（</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;
padding:0cm;background:white'>American National Standards Institute</span><span
style='font-family:宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>）在此基础上制定了一个</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:blue;border:none windowtext 1.0pt;padding:0cm;background:white'>C </span><span
style='font-family:宋体;color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言标准，于一九八三年发表。通常称之为</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:blue;border:none windowtext 1.0pt;padding:0cm;
background:white'>ANSI C</span><span style='font-family:宋体;color:blue;
border:none windowtext 1.0pt;padding:0cm;background:white'>。</span></p>

<p class=MsoNormal align=center style='text-align:center;line-height:16.5pt;
background:white'><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><img width=500 height=375 src="1.files/image001.jpg"><br>
</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";color:brown;
border:none windowtext 1.0pt;padding:0cm'>C</span><span style='font-family:
宋体;color:brown;border:none windowtext 1.0pt;padding:0cm'>语言之父</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:brown;border:none windowtext 1.0pt;
padding:0cm'>&#8212;&#8212;</span><span style='font-family:宋体;color:brown;border:none windowtext 1.0pt;
padding:0cm'>里奇</span></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'><br>
</span><span style='font-family:宋体;color:#555555;background:white'>在学习</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言之前，我们先了解一下</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的历史。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
<span style='background:white'>C</span></span><span style='font-family:宋体;
color:#555555;background:white'>语言是一门通用的，模块化，程序化的编程语言，被广泛应用于操作系统和应用软件的开发。由于其高效和可移植性，适应于不同硬件和软件平台，深受开发员的青睐。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>C</span></b><b><span style='font-size:12.0pt;font-family:宋体;
color:red;border:none windowtext 1.0pt;padding:0cm'>语言早期发展</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>1969 -
1973</span><span style='font-family:宋体;color:#555555;background:white'>年在</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> AT&amp;T </span><span style='font-family:宋体;color:#555555;background:
white'>贝尔实验室开始了</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'> C</span><span style='font-family:宋体;
color:#555555;background:white'>语言的最初研发。根据</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'> C</span><span
style='font-family:宋体;color:#555555;background:white'>语言的发明者丹尼斯</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>.</span><span style='font-family:宋体;color:#555555;background:white'>里奇</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> (<b><span style='border:none windowtext 1.0pt;padding:0cm'>Dennis
Ritchie</span></b>) </span><span style='font-family:宋体;color:#555555;
background:white'>说，</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'>C </span><span style='font-family:宋体;
color:#555555;background:white'>语言最重要的研发时期是在</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'> 1972 </span><span
style='font-family:宋体;color:#555555;background:white'>年。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;
border:none windowtext 1.0pt;padding:0cm;background:white'>C</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言之所以命名为</span></b><b><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>C</span></b><b><span style='font-family:宋体;color:green;
border:none windowtext 1.0pt;padding:0cm;background:white'>，是因为</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'> C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言源自</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'> Ken Thompson </span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>发明的</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'> B</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言，而</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'> B</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言则源自</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'> BCPL</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言。</span></b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
<br>
<span style='background:white'>C</span></span><span style='font-family:宋体;
color:#555555;background:white'>语言的诞生是和</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>UNIX</span><span
style='font-family:宋体;color:#555555;background:white'>操作系统的开发密不可分的，原先的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> UNIX</span><span style='font-family:宋体;color:#555555;background:white'>操作系统都是用汇编语言写的，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1973</span><span style='font-family:宋体;color:#555555;background:white'>年</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> UNIX</span><span style='font-family:宋体;color:#555555;background:white'>操作系统的核心用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言改写，从此以后，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言成为编写操作系统的主要语言。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>K&amp;R C</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>1978</span><span
style='font-family:宋体;color:#555555;background:white'>年</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>, Brian
Kernighan </span><span style='font-family:宋体;color:#555555;background:white'>和</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> Dennis Ritchie </span><span style='font-family:宋体;color:#555555;
background:white'>出版了一本书，名叫《</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'>The C Programming Language</span><span
style='font-family:宋体;color:#555555;background:white'>》</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>(</span><span
style='font-family:宋体;color:#555555;background:white'>中文译名为《</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>程序设计语言》</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>)</span><span style='font-family:宋体;color:#555555;background:white'>。这本书被</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言开发者们称为</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>&quot;K&amp;R&quot;</span><span style='font-family:宋体;color:#555555;
background:white'>，很多年来被当作</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'> C</span><span style='font-family:宋体;
color:#555555;background:white'>语言的非正式的标准说明。人们称这个版本的</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'> C</span><span
style='font-family:宋体;color:#555555;background:white'>语言为</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>&quot;K&amp;R C&quot;</span><span style='font-family:宋体;color:#555555;
background:white'>。</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
<br>
<span style='background:white'>1988</span></span><span style='font-family:宋体;
color:#555555;background:white'>年</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555;background:white'> Brian Kernighan </span><span
style='font-family:宋体;color:#555555;background:white'>和</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>
Dennis Ritchie </span><span style='font-family:宋体;color:#555555;background:
white'>修改此书，出版了《</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'>The C Programming Language</span><span
style='font-family:宋体;color:#555555;background:white'>》第二版，第二版涵盖了</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>ANSI C</span><span style='font-family:宋体;color:#555555;background:white'>语言标准。第二版从此成为大学计算机教育有关</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的经典教材，多年后也没再出现过更好的版本。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>ANSI C</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>1970</span><span
style='font-family:宋体;color:#555555;background:white'>到</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>80</span><span
style='font-family:宋体;color:#555555;background:white'>年代，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言被广泛应用，从大型主机到小型微机，也衍生了</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的很多不同版本。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>为统一</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言版本，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1983</span><span style='font-family:宋体;color:#555555;background:white'>年美国国家标准局</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> (American National Standards Institute</span><span style='font-family:
宋体;color:#555555;background:white'>，简称</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555;background:white'>ANSI)</span><span
style='font-family:宋体;color:#555555;background:white'>成立了一个委员会，来制定</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言标准。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1989</span><span style='font-family:宋体;color:#555555;background:white'>年</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言标准被批准，被称为</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> ANSI X3.159-1989 &quot;Programming Language C&quot;</span><span
style='font-family:宋体;color:#555555;background:white'>。这个版本的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言标准通常被称为</span><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;border:none windowtext 1.0pt;
padding:0cm;background:white'>ANSI C</span></b><span style='font-family:宋体;
color:#555555;background:white'>。</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>目前，几乎所有的开发工具都支持</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>ANSI C</span><span style='font-family:宋体;color:#555555;background:white'>标准。是</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言用得最广泛的一个标准版本。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>C99</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span style='font-family:
宋体;color:#555555;background:white'>在</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555;background:white'>ANSI C </span><span
style='font-family:宋体;color:#555555;background:white'>标准确立之后，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的规范在很长一段时间内都没有大的变动。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1995</span><span style='font-family:宋体;color:#555555;background:white'>年</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> WG14</span><span style='font-family:宋体;color:#555555;background:white'>小组对</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言进行了一些修改，成为后来的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> 1999</span><span style='font-family:宋体;color:#555555;background:white'>年发布的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> ISO/IEC 9899:1999</span><span style='font-family:宋体;color:#555555;
background:white'>标准，通常被成为</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'> C99</span><span style='font-family:宋体;
color:#555555;background:white'>。</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555'><br>
</span><span style='font-family:宋体;color:#555555;background:white'>但是各个公司对</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C99</span><span style='font-family:宋体;color:#555555;background:white'>的支持所表&#29694;出来的兴趣不同。当</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>GCC</span><span style='font-family:宋体;color:#555555;background:white'>和其它一些商业编译器支持</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C99</span><span style='font-family:宋体;color:#555555;background:white'>的大部分特性的&#26178;候，微软和</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> Borland</span><span style='font-family:宋体;color:#555555;background:
white'>却似乎对此不感兴趣。</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
<br>
</span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>C </span></b><b><span style='font-size:12.0pt;font-family:宋体;
color:red;border:none windowtext 1.0pt;padding:0cm'>语言对其它语言的影响</span></b></p>

<p class=MsoNormal><b><span style='font-family:宋体;color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>很多编程语言都深受</span></b><b><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'> C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言的影响，比如</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C++(</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>原先是</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言的一个扩展</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>)</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>，</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C#</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>，</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>Java</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>，</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>PHP, Javascript, Perl</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>，</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>LPC </span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>和</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'> UNIX </span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>的</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>C Shell</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>。</span></b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>也正因为</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言的影响力，掌握</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言的人，再学其它编程语言，大多能很快上手，触类旁通。接下来，我们开始具体讲解</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言。要学好一门编程语言，一定要边学边练，你要有一个</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'> C</span><span style='font-family:宋体;color:#555555;background:white'>语言的开发工具，在此教程中，我们使用微软的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>Visual Studio </span><span style='font-family:宋体;color:#555555;
background:white'>开发</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'>C</span><span style='font-family:宋体;color:#555555;
background:white'>语言程序。</span></p>

<p class=MsoNormal><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555;background:white'>&nbsp;</span></p>

<h1 align=center style='margin-top:3.75pt;margin-right:0cm;margin-bottom:7.5pt;
margin-left:0cm;text-align:center'><span lang=EN-US style='font-size:15.0pt;
line-height:240%;font-family:"Verdana","sans-serif";color:#2686CD'>C</span><span
style='font-size:15.0pt;line-height:240%;font-family:宋体;color:#2686CD'>语言是当代最优秀的程序设计语言</span></h1>

<p class=MsoNormal align=left style='text-align:left'><span style='font-family:
宋体;color:#555555;background:white'>早期的</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555;background:white'>C </span><span
style='font-family:宋体;color:#555555;background:white'>语言主要是用于</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>UNIX</span><span style='font-family:宋体;color:#555555;background:white'>系统。由于Ｃ语言的强大功能和各方面的优点逐渐为人们认识，到了八十年代，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>开始进入其它操作系统，并很快在各类大、中、小和微型计算机上得到了广泛的使用，成为当代最优秀的程序设计语言之一。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>下面，介绍一下</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的优秀之处：</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>1.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>语言简洁，使用方便灵活</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>C</span><span
style='font-family:宋体;color:#555555;background:white'>语言是现有程序设计语言中规模最小的语言之一，而小的语言体系往往能设计出较好的程序。</span><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言的关键字很少，</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>ANSI&nbsp;&nbsp;C</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>标准一共只有</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>32</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>个关键字，</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>9</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>种控制语句，压缩了一切不必要的成份。</span></b><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>C</span><span
style='font-family:宋体;color:#555555;background:white'>语言的书写形式比较自由，表达方法简洁，使用一些简单的方法就可以构造出相当复杂的数据类型和程序结构。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span></span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>2.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>可移植性好</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span style='font-family:
宋体;color:#555555;background:white'>用过汇编语言的读者都知道，即使是功能完全相同的一种程序，对于不同的单片机，必须采用不同的汇编语言来编写。这是因为汇编语言完全依赖于单片机硬件。而现代社会中新器件的更新换代速度非常快，也许我们每年都要跟新的单片机打交道。如果每接触一种新的单片机就要学习一次新的汇编语言，那么也许我们将一事无成，因为每学一种新的汇编语言，少则几月，多则上年，那么我们还有多少时间真正用于产品开发呢？</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;
border:none windowtext 1.0pt;padding:0cm;background:white'>C</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言是通过编译来得到可执行代码的，统计资料表明，不同机器上的</span></b><b><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言编译程序</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>80%</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>的代码是公共的，</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言的编译程序便于移植，从而使在一种单片机上使用的</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言程序，可以不加修改或稍加修改即可方便地移植到另一种结构类型的单片机上去。</span></b><span
style='font-family:宋体;color:#555555;background:white'>这大大增强了我们使用各种单片机进行产品开发的能力。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span></span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>3.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>表达能力强</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>C</span><span
style='font-family:宋体;color:#555555;background:white'>语言具有丰富的数据结构类型，可以根据需要采用</span><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>整型、实型、字符型、数组类型、指针类型、结构类型、联合类型、枚举类型</span></b><span
style='font-family:宋体;color:#555555;background:white'>等多种数据类型来实现各种复杂数据结构的运算。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言还具有多种运算符，灵活使用各种运算符可以实现其他高级语言难以实现的运算。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span></span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>4.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>表达方式灵活</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span style='font-family:
宋体;color:#555555;background:white'>利用</span><span lang=EN-US style='font-family:
"Tahoma","sans-serif";color:#555555;background:white'>C</span><span
style='font-family:宋体;color:#555555;background:white'>语言提供的多种运算符，可以组成各种表达式，还可采用多种方法来获得表达式的值，从而使用户在程序设计中具有更大的灵活性。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的语法规则不太严格，程序设计的自由度比较大，程序的书写格式自由灵活。程序主要用小写字母来编写，而小写字母是比较容易阅读的，这些充分体现了</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言灵活、方便和实用的特点。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span></span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>5.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>可进行结构化程序设计</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>C</span><span
style='font-family:宋体;color:#555555;background:white'>语言是以函数作为程序设计的基本单位的，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言程序中的函数相当于汇编语言中的子程序。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言对于输入和输出的处理也是通过函数调用来实现的。</span><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>各种</span></b><b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>C</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>语言编译器都会提供一个函数库，其中包含有许多标准函数，如各种数学函数、标准输入输出函数等。</span></b><span
style='font-family:宋体;color:#555555;background:white'>此外</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言还具有自定义函数的功能，用户可以根据自己的需要编制满足某种特殊需要的自定义函数。实际上</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言程序就是由许多个函数组成的，一个函数即相当于一个程序模块，因此</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言可以很容易地进行结构化程序设计。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span></span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>6.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>可以直接操作计算机硬件</span></b></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>C</span><span
style='font-family:宋体;color:#555555;background:white'>语言具有直接访问单片机物理地址的能力，可以直接访问片内或片外存储器，还可以进行各种位操作。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span></span></p>

<p class=MsoNormal align=left style='text-align:left;line-height:30.0pt;
background:white;vertical-align:middle'><b><span lang=EN-US style='font-size:
12.0pt;font-family:"Tahoma","sans-serif";color:red;border:none windowtext 1.0pt;
padding:0cm'>7.&nbsp;&nbsp;</span></b><b><span style='font-size:12.0pt;
font-family:宋体;color:red;border:none windowtext 1.0pt;padding:0cm'>生成的目标代码质量高</span></b></p>

<p class=MsoNormal><span style='font-family:宋体;color:#555555;background:white'>众所周知，汇编语言程序目标代码的效率是最高的，这就是为什么汇编语言仍是编写计算机系统软件的重要工具的原因。但是统计表明，对于同一个问题，用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言编写的程序生成代码的效率仅比用汇编语言编写的程序低</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>10%~20%</span><span style='font-family:宋体;color:#555555;background:white'>。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>&nbsp;</span><br>
</span><span style='font-family:宋体;color:#555555;background:white'>尽管</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言具有很多的优点，但和其他任何一种程序设计语言一样也有其自身的缺点，</span><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>如不能自动检查数组的边界，各种运算符的优先级别太多，某些运算符具有多种用途</span></b><span
style='font-family:宋体;color:#555555;background:white'>等。但总的来说，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言的优点远远超过了它的缺点。经验表明，程序设计人员一旦学会使用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>语言之后，就会对它爱不释手，尤其是单片机应用系统的程序设计人员更是如此。</span></p>

<h1 align=center style='margin-top:3.75pt;margin-right:0cm;margin-bottom:7.5pt;
margin-left:0cm;text-align:center'><span lang=EN-US style='line-height:240%;
font-family:"Tahoma","sans-serif";color:#555555;background:white'>&nbsp;&nbsp; </span><span
style='font-size:15.0pt;line-height:240%;font-family:宋体;color:#2686CD'>简单的</span><span
lang=EN-US style='font-size:15.0pt;line-height:240%;font-family:"Verdana","sans-serif";
color:#2686CD'>C</span><span style='font-size:15.0pt;line-height:240%;
font-family:宋体;color:#2686CD'>程序介绍</span></h1>

<p class=MsoNormal align=left style='text-align:left'><span style='font-family:
宋体;color:#555555;background:white'>为了说明Ｃ语言源程序结构的特点，先看以下几个程序。这几个程序由简到难，表现了Ｃ语言源程序在组成结构上的特点。虽然有关内容还未介绍，但可从这些例子中了解到组成一个</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>源程序的基本部分和书写格式。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>【例</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1.1</span><span style='font-family:宋体;color:#555555;background:white'>】</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>main()</span><br>
<span style='background:white'>{</span><br>
<span style='background:white'>&nbsp; printf(&quot;</span></span><span
style='font-family:宋体;color:#555555;background:white'>世界，您好！</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>\n&quot;);</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
<span style='background:white'>}</span><br>
<br>
</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>1.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>main</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>是主函数的函数名，表示这是一个主函数。</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>2.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>每一个</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>C</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>源程序都必须有，且只能有一个主函数</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:purple;border:none windowtext 1.0pt;
padding:0cm'>(main</span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>函数</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>)</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>。</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>3.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>函数调用语句，</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>printf</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>函数的功能是把要输出的内容送到显示器去显示。</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>4.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>printf</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>函数是一个由系统定义的标准函数，可在程序中直接调用。</span></p>

<p class=MsoNormal align=left style='text-align:left'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'><br>
</span><span style='font-family:宋体;color:#555555;background:white'>【例</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1.2</span><span style='font-family:宋体;color:#555555;background:white'>】</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<span style='background:white'>#include&lt;math.h&gt;</span><br>
<span style='background:white'>#include&lt;stdio.h&gt;</span><br>
<span style='background:white'>main()</span><br>
<span style='background:white'>{</span><br>
<span style='background:white'>&nbsp; double x,s;</span><br>
<span style='background:white'>&nbsp; printf(&quot;input number:\n&quot;);</span><br>
<span style='background:white'>&nbsp; scanf(&quot;%lf&quot;,&amp;x);</span><br>
<span style='background:white'>&nbsp; s=sin(x);</span><br>
<span style='background:white'>&nbsp; printf(&quot;sine of %lf is
%lf\n&quot;,x,s);</span><br>
<span style='background:white'>&nbsp;}</span><br>
<br>
</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>1.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>include</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>称为文件包含命令</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>2.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>扩展名为</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>.h</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>的文件称为头文件</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>3.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>定义两个实数变量，以被后面程序使用</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>4.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>显示提示信息</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>5.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>从键盘获得一个实数</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>x</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>6.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>求</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>x</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>的正弦</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:purple;border:none windowtext 1.0pt;
padding:0cm'>,</span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>并把它赋给变量</span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>s</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>7.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span style='font-family:宋体;color:purple;border:none windowtext 1.0pt;
padding:0cm'>显示程序运算结果</span></p>

<p class=MsoNormal align=left style='margin-left:0cm;text-align:left;
text-indent:-18.0pt;line-height:16.5pt;background:white'><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555'>8.<span
style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:purple;border:none windowtext 1.0pt;padding:0cm'>main</span><span
style='font-family:宋体;color:purple;border:none windowtext 1.0pt;padding:0cm'>函数结束</span></p>

<p class=MsoNormal><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
</span><span style='font-family:宋体;color:#555555;background:white'>程序的功能是从键盘输入一个数</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>x</span><span style='font-family:宋体;color:#555555;background:white'>，求</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>x</span><span style='font-family:宋体;color:#555555;background:white'>的正弦值，然后输出结果。在</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>main()</span><span style='font-family:宋体;color:#555555;background:white'>之前的两行称为预处理命令</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>(</span><span style='font-family:宋体;color:#555555;background:white'>详见后面</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>)</span><span style='font-family:宋体;color:#555555;background:white'>。</span><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>预处理命令还有其它几种，这里的</span></b><b><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>include </span></b><b><span style='font-family:
宋体;color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>称为文件包含命令，其意义是把尖括号</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>&lt;&gt;</span></b><b><span style='font-family:
宋体;color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>或引号</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>&quot;&quot;</span></b><b><span style='font-family:
宋体;color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>内指定的文件包含到本程序来，成为本程序的一部分。被包含的文件通常是由系统提供的，其扩展名为</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>.h</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>。因此也称为头文件或首部文件。</span></b><span
style='font-family:宋体;color:#555555;background:white'>Ｃ语言的头文件中包括了各个标准库函数的函数原型。因此，凡是在程序中调用一个库函数时，都必须包含该函数原型所在的头文件。在本例中，使用了三个库函数：输入函数</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>scanf</span><span style='font-family:宋体;color:#555555;background:white'>，正弦函数</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>sin,</span><span style='font-family:宋体;color:#555555;background:white'>输出函数</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>printf</span><span style='font-family:宋体;color:#555555;background:white'>。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>sin</span><span style='font-family:宋体;color:#555555;background:white'>函数是数学函数，其头文件为</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>math.h</span><span style='font-family:宋体;color:#555555;background:white'>文件，因此在程序的主函数前用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>include</span><span style='font-family:宋体;color:#555555;background:white'>命令包含了</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>math.h</span><span style='font-family:宋体;color:#555555;background:white'>。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>scanf</span><span style='font-family:宋体;color:#555555;background:white'>和</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>printf</span><span style='font-family:宋体;color:#555555;background:white'>是标准输入输出函数，其头文件为</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>stdio.h</span><span style='font-family:宋体;color:#555555;background:white'>，在主函数前也用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>include</span><span style='font-family:宋体;color:#555555;background:white'>命令包含了</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>stdio.h</span><span style='font-family:宋体;color:#555555;background:white'>文件。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><b><span style='font-family:宋体;color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>需要说明的是，</span></b><b><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>C</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>语言规定对</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>scanf</span></b><b><span style='font-family:宋体;
color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>和</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>printf</span></b><b><span style='font-family:
宋体;color:green;border:none windowtext 1.0pt;padding:0cm;background:white'>这两个函数可以省去对其头文件的包含命令。所以在本例中也可以删去第二行的包含命令</span></b><b><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>#include&lt;stdio.h&gt;</span></b><b><span
style='font-family:宋体;color:green;border:none windowtext 1.0pt;padding:0cm;
background:white'>。</span></b><span lang=EN-US style='font-family:"Tahoma","sans-serif";
color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>同样，在例</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1.1</span><span style='font-family:宋体;color:#555555;background:white'>中使用了</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>printf</span><span style='font-family:宋体;color:#555555;background:white'>函数，也省略了包含命令。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>在例题中的主函数体中又分为两部分，一部分为说明部分，另一部为分执行部分。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>说明是指变量的类型说明。例题</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>1.1</span><span style='font-family:宋体;color:#555555;background:white'>中未使用任何变量，因此无说明部分。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><b><span style='font-family:宋体;color:green;border:none windowtext 1.0pt;
padding:0cm;background:white'>Ｃ语言规定，源程序中所有用到的变量都必须先说明，后使用，否则将会出错。</span></b><span
style='font-family:宋体;color:#555555;background:white'>这一点是编译型高级程序设计语言的一个特点，与解释型的</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>BASIC</span><span style='font-family:宋体;color:#555555;background:white'>语言是不同的。说明部分是</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>C</span><span style='font-family:宋体;color:#555555;background:white'>源程序结构中很重要的组成部分。本例中使用了两个变量</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>x</span><span style='font-family:宋体;color:#555555;background:white'>，</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>s</span><span style='font-family:宋体;color:#555555;background:white'>，用来表示输入的自变量和</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>sin</span><span style='font-family:宋体;color:#555555;background:white'>函数值。由于</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>sin</span><span style='font-family:宋体;color:#555555;background:white'>函数要求这两个量必须是双精度浮点型，故用类型说明符</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>double</span><span style='font-family:宋体;color:#555555;background:white'>来说明这两个变量。说明部分后的四行为执行部分或称为执行语句部分，用以完成程序的功能。执行部分的第一行是输出语句，调用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>printf</span><span style='font-family:宋体;color:#555555;background:white'>函数在显示器上输出提示字符串，请操作人员输入自变量</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>x</span><span style='font-family:宋体;color:#555555;background:white'>的值。第二行为输入语句，调用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>scanf</span><span style='font-family:宋体;color:#555555;background:white'>函数，接受键盘上输入的数并存入变量</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>x</span><span style='font-family:宋体;color:#555555;background:white'>中。第三行是调用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>sin</span><span style='font-family:宋体;color:#555555;background:white'>函数并把函数值送到变量</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>s</span><span style='font-family:宋体;color:#555555;background:white'>中。第四行是用</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>printf </span><span style='font-family:宋体;color:#555555;background:white'>函数输出变量</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>s</span><span style='font-family:宋体;color:#555555;background:white'>的值，即</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>x</span><span style='font-family:宋体;color:#555555;background:white'>的正弦值。程序结束。</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555'><br>
<br>
</span><span style='font-family:宋体;color:#555555;background:white'>运行本程序时，首先在显示器屏幕上给出提示串</span><span
lang=EN-US style='font-family:"Tahoma","sans-serif";color:#555555;background:
white'>input number</span><span style='font-family:宋体;color:#555555;background:
white'>，这是由执行部分的第一行完成的。用户在提示下从键盘上键入某一数，如</span><span lang=EN-US
style='font-family:"Tahoma","sans-serif";color:#555555;background:white'>5</span><span
style='font-family:宋体;color:#555555;background:white'>，按下回车键，接着在屏幕上给出计算结果。</span></p>

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